A group of scientists from the ITMO University in Saint Petersburg had recently published an article detailing a new technique for making hologram images by means of an ordinary inkjet printer, expected to be significantly less costly and time-consuming than current methodologies.
The group, led by Alexander Vinogradov, a Senior Research Associate at the university‘s International Laboratory of Solution Chemistry of Advanced Materials and Technologies (SCAMT), developed a colourless ink made of nano-crystalline titania that can be loaded into an inkjet printer and then deposited on special micro-embossed paper and covered in varnish, resulting in unique patterned images.
Thanks to the new technique, vivid holographic images can now be printed on transparent film in a matter of minutes instead of days, as with the use of conventional methods.
Introduced for the first time in the 1960s, rainbow holograms are widely used to fight against forgery of credit cards, bank notes, documents and certain manufactured products that call for a high level of protection.
According to Aleksandr Yakovlev, first author on the study and researcher at SCAMT, making holograms the usual way takes an incredibly long time and consists of several distinct stages that call for a set of requirements, such as temperature control and isolating vibration, which complicate the process even further.
“First, one needs to create a master hologram, which is usually laser recorded on a thin layer of photosensitive polymer. The polymer is then dried and washed out to get rid of unexposed parts. The resulting stencil is then transferred to a metallic matrix, which eventually serves to emboss holographic micro-relief on the surface of a transparent polymer film.”
One peculiar thing about the new ink is its high refractive index in all visible ranges of light, which helps in preserving the rainbow holographic effect after the application of varnish (or a layer of polymer) is completed.
The team claims that making holograms with inkjet printers could cut the cost by several times, allow for the rendering of images of any size, and, finally, lead to the creation of unique custom holograms in a matter of minutes.
The paper was published on November 17 in the science journal Advanced Functional Materials.